Swimming Speed Of Larvae Research Articles

Heritability of dispersal-related larval traits in the clown anemonefish Amphiprion percula.

A major goal of marine ecology is to identify the drivers of variation in larval dispersal. Larval traits are emerging as an important potential source of variation in dispersal outcomes, but little is known about how the evolution of these traits might shape dispersal patterns. Here, we consider the potential for adaptive evolution in two possibly dispersal-related traits by quantifying the heritability of larval size and swimming speed in the clown anemonefish (Amphiprion percula). Using a laboratory population of wild-caught A. percula, we measured the size and swimming speed of larvae from 24 half-sibling families. Phenotypic variance was partitioned into genetic and environmental components using a linear mixed-effects model. Importantly, by including half-siblings in the breeding design, we ensured that our estimates of genetic variance do not include nonheritable effects shared by clutches of full-siblings, which could lead to significant overestimates of heritability. We find unequivocal evidence for the heritability of larval body size (estimated between 0.21 and 0.34) and equivocal evidence for the heritability of swimming speed (between 0.05 and 0.19 depending on the choice of prior). From a methodological perspective, this work demonstrates the importance of evaluating sensitivity to prior distribution in Bayesian analysis. From a biological perspective, it advances our understanding of potential dispersal-related larval traits by quantifying the extent to which they can be inherited and thus have the potential for adaptive evolution.

Toxicity evaluation of graphene oxide on cysts and three larval stages of Artemia salina

Using Artemia salina as an experimental model, the potential risks of graphene oxide (GO) to marine ecosystems were investigated. Hatchability of capsulated and decapsulated cysts, mortality of instar I, II and III larvae, and a number of morphological, ethological and physiological parameters were selected as end-points for toxicity assessment. Our results show that GO significantly decreased (p<0.01) the hatchability of capsulated and decapsulated cysts following exposure to 400 and 600mg/L for 36h. There was a concentration-dependent increase in mortality and decrease in swimming speed of larvae, and instar II larvae showed a greater sensitivity compared with instar I and instar III larvae. The LC50 values of instar II and III were 368.18 and 387.68mg/L, respectively (not calculable for instar I). The EC50 values for swimming speed alteration of instar I, II and III were 415.13, 273.50 and 289.05mg/L, respectively. Moreover, body lengths and individual dry weight of larvae (instar I, II and III) also decreased in dose-dependent manners. GO attached onto the surface of cysts and larvae, resulting in irreversible damage to the larval body surface. All of malondialdehyde content, total antioxidant capacity, reactive oxygen species and superoxide dismutase activity of A. salina larvae substantially increased in dose-dependent manners after exposure to GO suspensions, indicating that toxic effects were due to oxidative damages. However, for the activities of catalase, glutathione peroxidase and glutathione S-transferase, GO induced different effects on the larvae. Finally, the uptake result indicated that GO was ingested and concentrated in the gut, and was visible within the primary body cavity and yolk.

Critical swimming speeds of late-stage coral reef fish larvae: variation within species, among species and between locations

The swimming abilities of larval fishes are important for their survival, potentially affecting their ability to avoid predators, obtain food and control dispersal patterns. Near settlement swimming abilities may also influence spatial and temporal patterns of recruitment. We examined Critical speed (U-crit) swimming ability in late stage larvae of 89 species of coral reef fishes from the Great Barrier Reef and the Caribbean. Coefficients of variation in U-crit calculated at the individual level were high (28.4%), and this was not explained by differences in size or condition factor of these same larvae. Among species U-crit ranged from 5.5 cm s−1 to 100.8 cm s−1 (mean=37.3 cm s−1), with 95% of species able to swim faster than the average current speed around Lizard Island, suggesting that most species should be capable of influencing their spatial and temporal patterns of settlement. Inter-specific differences in swimming ability (at both the family and species levels) were significantly correlated with size and larval morphology. Correlations were found between swimming performance and propulsive area, fineness ratio and aspect ratio, and these morphological parameters may prove useful for predicting swimming ability in other taxa. Overall, the swimming speeds of larvae from the same families at the two locations were relatively similar, although the Lutjanidae and Acanthuridae from the Caribbean were significantly slower than those from the great barrier reef. Differences in swimming speed and body form among late stage larvae suggests that they will respond differently to factors influencing survival and transport during their pelagic phase, as well as habitat use following settlement.

Behavior of larval Hemigrapsus sanguineus (de Haan) in response to gravity and pressure

Hemigrapsus sanguineus is an invasive species of crab (family: Grapsidae) in the north Atlantic basin. The species has spread rapidly since it was first discovered in North America in the late 1980s; however, the mechanisms of this range expansion remain unclear. This study attempts to predict the vertical distribution and, thus, ultimate transport of H. sanguineus larvae by examining larval responses to gravity and pressure. Geotaxis was determined by measuring the response of individual larvae to gravity in the absence of other tactic stimuli. Barokinesis was determined by measuring changes in swimming speed of larvae upon step-wise changes in pressure. Geotactic response of the larvae changes ontogenetically; early stage larvae are negatively geotactic (orienting towards the surface), while late stage larvae are positively geotactic (orienting towards the bottom). Larvae show a response to pressure that would aid in depth regulation. Early-stage larvae increase activity upon a change in pressure and orient their movement to gravity. However, the larvae show a relatively low sensitivity to pressure change. The evidence predicts an export-and-return model of larval transport, similar to that of Uca spp. in the Middle Atlantic Bight. This model supports the hypothesis that H. sanguineus larvae have the potential for high dispersal and will continue to invade new regions through larval transport.

In situ swimming and settlement behaviour of larvae of an Indo-Pacific coral-reef fish, the coral trout Plectropomus leopardus (Pisces: Serranidae)

Late larvae of the serranid coral trout Plectropomus leopardus (Lacepede), captured in light traps, were released during the day both in open water and adjacent to two reefs, and their behaviour was observed by divers at Lizard Island, northern Great Barrier Reef. Coral trout larvae (n = 110) were present in light-trap catches from 18 November to 3 December 1997, including new moon (30 November). The swimming speed of larvae in open water or when swimming away from reefs was significantly greater (mean 17.9 cm s−1) than the speed of larvae swimming towards or over reefs (mean 7.2 cm s−1). Near reefs, larvae swam at average depths of 2.7 to 4.2 m, avoiding 0 to 2 m. In open water, swimming depth varied with location: larvae >1 km east of Lizard Island swam steeply downward to >20 m in 2 to 4 min; larvae >1 km west oscillated between 2.6 and 13 m; larvae 100 to 200 m east of Lizard Island oscillated between 0.8 and 15 m. Nearly all larvae swam directionally in open water and near reefs. In open water, the average swimming direction of all larvae was towards the island, and 80% (4 of 5) swam directionally (p < 0.05, Rayleigh's test). Larvae swam directionally over the reef while looking for settlement sites. The frequency of behaviours by larvae differed between two reefs of different exposure and morphology. Depending on site, 26 to 32% of larvae released adjacent to reefs swam to open water: of these, some initially swam towards or over the reef before swimming offshore. In some cases, offshore-swimming seemed to be due to the presence of predators, but usually no obvious cause was observed. Depending on the reef, 49 to 64% of the larvae settled. Non-predatory reef residents aggressively approached 19% of settlers. Between 5 and 17% of the larvae were eaten while approaching the reef or attempting to settle, primarily by lizardfishes but also by wrasses, groupers and snappers. A higher percentage of larvae settled in the second week of our study than in the first. Average time to settlement was short (138 s ± 33 SE), but some larvae took up to 15 min to settle. Average settlement depth was 7.5 to 9.9 m, and differed between locations. No settlement took place on reef flats or at depths <4.2 m. Larvae did not appear to be selective about settlement substrate, but settled most frequently on live and dead hard coral. Late-stage larvae of coral trout are capable swimmers with considerable control over speed, depth and direction. Habitat selection, avoidance of predators and settlement seem to rely on vision.

Influence of temperature and ambient oxygen on the swimming energetics of cyprinid larvae and juveniles

The relationship between respiration and swimming speed of larvae and juveniles (2–100 mg fresh mass) of Danube bleak, Chalcalburnus chalcoides (Cyprinidae), was measured at 15° and 20° C under hypoxic (50% air saturation), normoxic, and hyperoxic (140% air saturation) conditions. In a flow-tunnel equipped with a flow-through respirometer the animals swam at speeds of up to 8 lengths · s-1; speeds were sustained for at least two minutes. The mass specific standard, routine, and active respiration rates declined with increasing body mass at both temperatures. Metabolic intensity increased with temperature, but also the critical swimming speed (at which oxygen uptake reached its maximum) was higher at 20° than at 15° C by about 30%. Nevertheless, the oxygen debt incurred by the fish at the highest speeds was about 40%, and the net cost of swimming about 32%, lower at 20° than at 15°C. The standard metabolic rate was more strongly dependent on temperature (Q10 around 2.5) than the maximum active rate (Q10 below 2). Whereas standard and routine respiration rates were well regulated over the pO2-range investigated (8.5–25.8 kPa), the active rates showed a conformer-like pattern, resulting in factorial scopes for activity between 2 and 4. Under hypoxia, the critical swimming speed was lower than under normoxia by about 1.51 · s-1, but the net cost of swimming was also lower by about 30%. On the other hand, hyperoxia neither increased the swimming performance nor did it lead to a further increase of the metabolic cost of swimming. The hypoxia experiments suggest that in response to lowered tensions of ambient oxygen maintenance functions of metabolism not directly related to swimming may be temporarily reduced, leading to increased apparent swimming efficiency under these conditions. The responses of the larvae of Danube bleak to low temperature and low ambient oxygen are discussed in terms of the metabolic strategies by which energy-limited animals meet the challenge of environmental deterioration.

Effect of hatching time on larval mortality and survival of the prawn Macrobrachium idae

The prawn Macrobrachium idaeHeller carries 40 to 160 eggs depending upon the body size of the mother animal. After incubation, 63, 35 and 2% eggs are hatched on the first, second and third hatching nights, respectively. Mean dry weight of a single larva relased on the first night is 420 μg (equivalent to 2.86 cal). Larvae released on the second or third hatching nights weighed 380 μg (=2.56 cal) or 308 μg (=2.02 cal). The total reserve yolk-energy available in a larva hatched on the first night is 1 cal. There is a definite shift from protein to fat metabolism as hatching is delayed. Oxygen consumption of developing eggs awaiting release on the first or second hatching night is 1.9 μl/mg dry weight/h. In comparison to larvae released on the first night, those released on the second night exhibit 2% increase in total body-length and 2.4 or 14.3% decrease in the lengths of the 6th abdominal segment or the orbit. Larvae released on the first, second or third hatching nights, on exposure to starvation stress, survive for 3.8, 2.3 or 1.5 days. The swimming speed of larvae released on the first or second night is 1.0 or 0.6 cm/sec. Larvae released on the subsequent hatching nights committed nearly 2 times greater number of mistakes per cm distance in the horizontal plane. Since hatching of all developing eggs simultaneously on the first hatching night is possible by means of artificial technique(s), it is possible to “improve” survival rate of decapod larvae.